More doubt on virus, chronic fatigue connection

There is more evidence that a virus once thought to be linked to chronic fatigue syndrome was a false alarm. A U.S. study released Thursday concluded lab tests used to make that link are unreliable.

Also Thursday researchers were withdrawing part of the original study that suggested the connection — although not its conclusions — because a laboratory that contributed to the work discovered contamination in some of its samples.

In 2009, researchers in the state of Nevada announced they had found a mouse-related virus named XMRV in the blood of chronic fatigue patients, fueling hopes that a cause of the mysterious illness might have been found. Blood banks began turning away donations from people diagnosed with chronic fatigue. Yet numerous other studies failed to confirm the findings. Last spring, Science declared any link "seriously in question" as genetic tracing suggested it was the result of laboratory contamination.

The newest study was part of government efforts to see if XMRV or related viruses might affect the safety of the blood supply. It concluded there's no reason to worry.

Nine laboratories re-tested blood samples from 30 people, some chronic fatigue patients previously reported to have XMRV and some healthy people known to be virus-free. Only the two labs that previously reported an XMRV link could find any signs of the virus in some samples — but some of those were from healthy people, and additional testing couldn't confirm the findings.

"There does not seem to be any evidence of an association of XMRV with chronic fatigue syndrome," said Dr. Harvey Klein, who was not part of the new research but monitors it for the international blood-banking association AABB. Still, blood banks may continue turning away chronic fatigue patients out of concern about their own health after losing blood, he added.

The controversy is not over. In a statement, researchers at Nevada's Whittemore Peterson Institute said, "We want to make it very clear that we are continuing the important work" of studying the virus, despite the partial retraction of their 2009 study.